Forensic Toxicology is the branch of science which determines the absence or presence of drugs and their metabolites, chemicals such as ethanol and other volatile substances, and other drugs of abuse in human fluids and tissues. The presence of these substances may then be evaluated to determine their role as a contributory factor in modifying human performance or behavior or in the cause and manner of death. The Toxicology Section analyzes biological samples for the presence alcohol and other volatile substances as well as for various drugs, including both illicit and prescription substances. This analysis is essential in investigation of driving under the influence offenses such as DWI, criminal vehicular operation and homicides, and drug facilitated sexual assaults. It can also assist medical examiners and coroners in determining a cause of death in cases where circumstances surrounding the death may be unknown or unclear. 

Samples submitted for toxicological analysis are collected in the field, generally by law enforcement or a Sexual Assault Nurse Examiner (SANE). Blood samples must be collected by trained personnel such as a physician, nurse, medical technologist, phlebotomist, laboratory assistant or other qualified personnel. Some law enforcement officers are trained as phlebotomists and can perform this service for their agency, but most collections are done in a hospital or clinic setting. The collection kits used for both blood and urine specimens are provided to law enforcement by the BCA Forensic Science Services. Other biological specimens not collected in these kits can also be analyzed.